The more you can afford to spend on nitrous toys the nicer it will be. Been down that road. By the time you get done spending on setting up all the nitrous bling the way you want it, you'll be into it the cost of FI, but you'll still be filling a bottle (or two). 150 shot is entry level blower. P1SC, V2SQ, 2200SL will all give you that right out of the gate with room to grow.
If you have the discipline and restraint to just run a simple nitrous kit with a fuel pump upgrade, and use it as intended, you can make good power and be punishing on the track. A basic kit has serious limitations and inconsistencies, however. I haven't met anyone who played with nitrous that ever stopped at a "kit." I bought my kit used from this forum, he started with nitrous and kept adding on until he realized the next step was blower money, ended up selling the kit for a fraction of its retail, nitrous parts are probably the worst for depreciation. Even having acquired my kit for 1/4 the retail cost, I still sunk more and more money into it, tailoring the setup to my needs. It wasn't enough having a bottle in the trunk. I needed remote access to the bottle, so I could turn it on and off on the fly. ($Cha-Ching$). Now I had supply on demand, but I still had to wait for the bottle to cook to 1100psi before it was efficient, this wouldn't do. Enter the piggy-back system using a Nitrogen bottle to pressurize the Nitrous bottle. I now had two bottles to fill with two entirely different gases. Another mounting setup, slew of fittings and lines. ($$Cha-Ching$$). For a while I had gotten away with running the stock fuel pump on a BAP to bridge the gap for fuel. Now that I had instant bottle pressure whenever I wanted, I needed to make sure the fuel spikes didn't kill the motor. Only a dedicated fuel supply would do... and if it's going to be dedicated, why not bump the octane up to 100 just for good measure. 1 gallon fuel cell, in-line fuel pump, return-style with fuel regulator fed to the fuel solenoid, more wiring and electronics, custom fuel jetting. ($$$Cha-Ching$$$). Now I had 125 shot on demand. As long as nitrous was in the bottle, it was always there, whenever I wanted at the drop of a hat. WRX Psssh at me, I Psshhh right back. Camaro start putting a door on me, grab the switch, tables turned. I could get about 13-15 good solid uses out of a standard nitrous bottle thanks to the piggy-back system, nitrous was good to the last drop and bottle pressure was *always* 1100psi from start to finish, unlike the bottle heater method. Had the setup for about 2 months, went to hit it for giggles one night on the way home and got nothing but 100 octane and nitrogen, LOL. Saw a Procharger D1SC kit on craigslist for $2200, ($1200 less than what I had into my nitrous setup) said, "No more renting power." Mind you, all the nitrous toys stayed in the car even after the blower was installed, I always figured if I ever *really* wanted a hit of the bottle crack, it was still there. Never did though. 485wtq was always plenty. Always there. Consistent.
A nitrous kit with a 150 shot is just the tip of the iceberg.
